How do i do i'm just kind of confused

Last month, a 770 g box of cereal was sold at a grocery store for $3.10. however, this month, the cereal manufacturer launched the same cereal in a 640 g box, which is being sold at $2.50. what is the percent change in the unit price?

Put the following steps for calculating net worth in the correct order

Me d is also an option but i couldn't get it in the picture